In many cases mojoPortal will default to the culture of the browser. It's likely that because you have a chinese version of windows, you also have a chinese version of internet explorer.
You can change the browser default (different browsers will obviously have different options for this), or you can force a specific culture (which should override the browser default for all users of the site as well, so it will always be the culture you specify regardless of the region where the user views it from).
Hope this helps,
-Isaac